mined :— (100), (010), (001), (110), (102), (101); 

 Figure 14 is a clinographic projection of the cry 



Fig. 14— Clinographic drawing of barytes from Dundas quarry. 

 Bitumen. — It lias been reported to me that bitumen 

 occurs in the Dundas neck, though I have not yet seen it 

 myself. It is, however, frequent in the Hornsby breccia. 

 It forms small patches or filling little cracks perhaps two 

 or three inches in length. It is generally associated with 

 and frequently traversed by little veinlets of calcite. Held 

 in a flame it swells up and froths, but burns away with a 

 smoky flame leaving only a trace of ash. It has doubtless 

 been distilled out of the coal seams below as is the case of 

 the bitumen in the Mittagong syenite. 1 



Before attempting to account for the origin and presence 

 of the basic and ultrabasic inclusions in the Dundas and 

 Hornsby necks, it will be well to glance briefly at some 

 other occurrences of the inclusions in New South Walts and 

 elsewhere. Rocks similar to those here described are found 

 in a monchiquite dyke at Kiamu" and also at Cerrin.^ong. 

 These monchiquites are members of a series of dykes which 

 cut through the alkaline Pernio Carboniferous volcanic 

 series and intrude also the Triassic Narrabeen series. They 

 are newer than some olivine basalt dykes, and perhaps, 



